Natural Radioactivity Measurements and Radiation Dose Assessments in Different Environmental Samples from Qena Governorate, Upper Egypt

Abstract

This study evaluates the specific activity and radiological hazards of primordial radionuclides (²²⁶Ra, ²³²Th, ⁴⁰K) in soils from five regions in Qena Governorate, Upper Egypt, and in chemical fertilizers using NaI(Tl) gamma-ray spectrometry. The soil activity concentrations (Bq/kg) spanned (4 ± 0.2)–(47 ± 2.3) for ²²⁶Ra, (6 ± 0.3)–(58 ± 3) for ²³²Th, and (14 ± 0.7)–(284 ± 14) for ⁴⁰K, with ⁴⁰K dominating in all samples except one from Qift. Fertilizers exhibited higher variability (Bq/kg): ²²⁶Ra (42 ± 2)–(169 ± 8), ²³²Th (32 ± 4)–(99 ± 4.9), and ⁴⁰K (30 ± 1.5)–(638 ± 32). Phosphate rocks from Umm al-Huwaitat showed moderate activity: (25 ± 4)–(203 ± 10 )Bq/kg. The average radiological indices for soils were 70.7 Bq/kg (Ra_eq) and 0.19 (H_ex), being well below global thresholds (370 Bq/kg; H_ex < 1). The annual effective dose equivalents (AEDE) for Qena soils were 0.039 µSv/year (outdoor) and 0.156 mSv/year (indoor), representing 3.9% and 15.6% of the ICRP (1990) public limit (1 mSv/year). Fertilizer Ra_eq values (168.6–251.9 Bq/kg) exceeded those of soils but remained within safe limits. The average excess lifetime cancer risk (ELCR) for soils was 0.69 × 10^–3, i.e., 47% of the global average (1.45 × 10^–3), and that for fertilizers reached 2.13 × 10^–3, being within negligible risk thresholds. The results align with global benchmarks, confirming minimal public and environmental radiological risks. The study establishes critical baseline data for monitoring population exposure and guiding agricultural practices in regions utilizing phosphate-based fertilizers. These findings underscore the importance of continued radiological surveillance in areas with intensive fertilizer use to ensure long-term safety.